A Phoenix TV station says its investigation of a local drug bust three months ago involving four illegal aliens turned up 43 weapons that had been sold legally to “straw purchasers” in Arizona but wound up in the hands of Mexican drug cartels — all under the watchful eyes of the US Bureau of Alcohol, Tobacco, Firearms and Explosives.

And that’s not all.

A search of court and ATF documents turned up at least four other local cases in which major drug busts also involved numerous assault rifles on the agency’s Suspect Gun Database.

That such weapons are turning up in drug cases north of the border is hardly surprising.

What’s outrageous is that two of them have been linked to an Arizona shootout in which Customs and Border Protection Agent Brian Terry was killed.

Yet when several agents — appalled by a program that knowingly sent as many as 2,500 deadly weapons south (only a few hundred of which have been recovered) — tried to blow the whistle after Terry’s death, their allegations were ignored by the Justice Department.

So guess who’s in charge of investigating this monumental disaster?

Justice’s inspector general.

As Sen. Charles Grassley (R-Kan.) notes, ATF officials cited a critical report by that same IG’s office about the larger Project Gunrunner “as one of the factors that prompted the shift to a riskier strategy of letting guns be trafficked rather than arresting straw buyers.”

Which, he adds, “could create an incentive [for the IG] to minimize the significance of the allegations.”

President Obama was basically close-mouthed when asked about the scandal at his recent press conference, other than expressing his confidence that Attorney General Eric Holder “would not have ordered gunrunning to be able to pass through into Mexico.”